US2212269A

US2212269A - Protective coated article

Info

Publication number: US2212269A
Application number: US239670A
Authority: US
Inventors: Henry L Kohler
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-11-09
Filing date: 1938-11-09
Publication date: 1940-08-20
Anticipated expiration: 1957-08-20

Description

Aug 20, 1940- H. l.. KOHLER A 2,212,269

PROTECTIVE COATED ARTICLE Filed Nov. 9, 1938 ZINC COAT/N6 6 SHEET .STEEL Z /N C -MERCUR AMALGAM COA TlNG ZINC CAT/NGV ZINC C OA TING i Z/Nc -MERC URY AMALGAM COAT/NG INVENTOR HENRY l.. KOHLER BY ATTORNEY Patented Aug. 20, 1940 UNITED STATES PATENT OFFICE Andrew A. Kramer,

Kansas City, Mo.

Application November 9, 1938, Serial No. 239,670

6 Claims.

My invention relates to protective coated articles, and more particularly to sheet metal articles provided with a protective coating. This application is a continuation in part of my copending aplication Serial No. 144,029, filed May 21, 1937, patented March 21, 1939, Patent No. 2,150,929.

A diculty that has always existed in the utilization of galvanized metallic sheets for making certain articles out of the same, has been that the galvanizing coating is not sufficiently resistant to corrosion under certain conditions to make the practical use thereof possible. An attempt to overcome this diiiculty has been made by providing a heavier galvanizing coating on the sheet. The heavy zinc coating thus provided, however, has the disadvantage that, when the sheet is bent, the coating at the bend would crack and tend to peel or flake oil". As a result, although the.' sheet as a whole was provided with a heavy galvanizing coating' over its er1-tire surface before being fabricated, the bending of a sheet to form a flange or a seam thereon, frequently damaged the galvanizing coating on the sheet so seriously that it would render the coat.- ing partially ineffective, on the Outside of the bends required to form the anges, or seams. Consequently the advantage of the heavy galvanizing coating on the sheet was largely lost, this being true because, at the point at which the galvanizing coating was caused to be damaged, or ruptured, by bending, the sheet would be, for practical purposes, no better than an uncoated sheet, as far as resistance to oxidization, `or other corrosion, was-concerned. While many attempts have been made to overcome this diculty, by a hot dipping process after the article has been formed from the galvanized sheet, for example, this is diflicult to accomplish and requires expensive equipment, if any large sheet metal article is to be galvanized after fabrication by such a dipping process.

It is a purpose of my invention to provide means for overcoming the above mentioned difculty with galvanized sheets having a heavy coating of zinc thereon, and at the same time to provide a sheet that is more resistant to corrosion over the entire area thereof, if this is desired, than is possible with ordinary zinc coatings provided by a galvanizing process. I accomplish this by providing a mercury-zinc amalgam coating on the sheet, which is applied y to any area thereof that may be desired.

My improved protective coating may be utilized 5g to give better protection than zinc against certain types of corrosion, or corrosion due to certain causes, either over the entire area of a metallic sheet, or over the entire area of one side thereof, or over the entire area of a fabricated sheet metal section, or one side of such 5 a section, if this should be desired,` and is particularly adapted for use at and adjacent the bends in a fabricated sheet, whereby any rupture in the galvanizing coating that may have occurred during fabrication, from any of the 10 fabrication steps, will be closed and the sheet protected at such bends, or other fabricated p0rltions thereof, more effectively than was the case before the bending, or other operation, thereon, that damaged, or ruptured, the protective zinc coating on the sheet originally.

It is a further purpose of my invention to provide a protectivev coating of a zinc-mercury amalgam that has the same appearance as the zinc coating originally on the sheet as obtained 20 by the galvanizing process. Galvanized metallic sheets have a characteristic Spangled appearance.

It is highly desirable to maintain this Spangled appearance of the sheet after my improved coating has been plac'ed thereon. This is accom- 25 plished by utilizing a paste-like zinc-mercury amalgam, which is applied to the sheet in a manner that the structural characteristics of the zinc coating on the sheet are not changed. My improved protective coating will resist every 30 kind of corrosion equally as well, as does the galvanized sheet before having the treatment `ythereof, whereby my improved coating is produced, and for most uses, will produce acoating that will be more resistant to corrosion than the 35 heavy galvanizing coating applied to such sheets, or fabricated sheet metal sections. As the term fabrication is used herein, it means any bending, cutting or punching operation, or any other operation on a sheet, that may be performed 40 thereon after the same has been rolled and galvanized.

Other objects and advantages of my invention will appear as the description of the same proceeds. I desire to have'it understood, however, 45 that I do not intend to limit myseif to the particular details` described, except as defined in the claims.

In the drawing:

Fig. 1 is a fragmentary sectional view on a greatly enlarged scale, showing my improved amalgam coating applied to a sheet having a bend therein, and

Fig. 2 is a similar view, showing my improved 55 amalgam coating applied to av sheet otherwise fabricated than by bending.

Referring in detail tothe drawing, in Figs. 1 and 2 the metallic body portion of the sheet, which is usually steel or iron, is indicated by the numeral 3. The sheet shown in Fig. 1 is bent at 4 and the bend may cause damage to the zinc coating ordinarily on the galvanized sheet on the outer side of the bend substantially at the outer corner thereof. The zinc coatingprovided on the sheet is indicated by the numeral 5 and the amalgam coating around the outside of the bend and adjacent said bend in the sheet is indicated in Fig. 1 by the numeral 6. i

In Fig. 2 the same numerals are applied to the zinc coating and the amalgam coating, but instead of showing a sheet'with a bend therein, the sheet is shown as being fabricated by punching a hole 1 therein, this being merely illustrative of some fabrication operation that may be performed on the sheet that may damage the ordinary zinc galvanizing coating thereon.

My improved protective coating is provided on galvanized sheets that have been fabricated to the desired size and shape, by bending, die-shaping, cutting and'punching operations, or any of these that' may be necessary to produce the article, or sections of an article, of the desired shape from the galvanized sheet of metal. After the sheet has been fabricated, it is cleaned at the places at which the protective coating is to be provided thereon, usually by means of dilute hydrochloric acid, or a solution of tin chloride, or antimony chloride, or lead chloride, or zinc chloride, or cyanide of soda. This cleaning solution may be applied with a brush or swab of some character, and the excess may be removed with a cloth,

' or any other suitable means. When it is desired to apply the protective coating only at or adjacent a ruptured area on a galvanized sheet, or an area that may have been damaged to the extenty of injuringthe protective coating, or rupturing the same, the galvanized sheets are cleaned only on the outer sides of all bends therein, or any other area at which the coating may have been ruptured, or damaged, and areas adjacent these bends, or other areas where the damage may have occurred. A zone at the place at which the rupture in the zinc coating may exist will thus be cleaned, and also a zone on each side thereof.

A putty-like amalgam of mercury and zinc is made up prior to cleaning the sheets, or is made up in quantity to be used whenever necessary, said amalgam having such proportions of zinc and mercury therein as to produce a soft putty-like material of the consistency of thick paste or cream. 'I'he proportions of zinc and mercury that are used to produce this soft putty-like material will vary somewhat, dependent upon the atmospheric temperature existing, as the material must, of course, be of the soft, creamy putty-like character at the temperature at which it is applied to the sheet. Thus in the winter time, when a lower temperature is encountered, both in the atmosphere and in the material of the sheets themselves, a larger proportion of the mercury to the zinc must be used to produce this soft putty-like coating material. I have found that 15% zinc and mercury by weight will produce an amalgam of the desired consistency in the summer time, while in the winter time, when the temperatures are exceedingly low, it is necessary to utilize an amalgam made for this purpose that will have as little as 10% zinc by weight, and mercury by weight, while, if the mercury is heated while the zinc is being incorporated therein, the percentage of zinc can be increased to 20% by weight to 80% by weight of mercury. The relative proportions of the metal, or metals, amalgamating with mercury that have to be utilized depend upon the melting points of the metals that are amalgamated with mercury and the temperature encountered, and the heating makes it possible to incorporate a larger amount of the metal amalgamating with the mercury, than would otherwise be the case. There is no advantage in incorporating too large a percentage of zinc in the amalgam, however, as it must, of course, remain of a creamy character, or a puttylike character, at the temperature at which it is applied to the sheet, and if too large a percentage of zinc is included in the amalgam by adding the zinc to the heated mercury, it will not have the desired consistency at the temperature at which it is to be utilized.

The zinc can be in the form of any small particles, such as shavings,y turnings, cuttings, or in the form of a powder or granules. The nely divided zinc is stirred into the quantity of mercury that is to be utilized to make the amalgam in the proportions necessary, substantially within the limits above referred to. This is ordinarily done without heating the mercury, but the mer' cury may be heated to incorporate a somewhat larger percentage of zinc in the amalgam than would otherwise be possible within the limits pointed out above. Care must, of course, be utilized in doing this, that the mercury is not heated to a temperature near the vaporization point thereof.

The soft putty-like amalgam of zinc and mercury, produced as above described, is applied to the cleaned zone, or area, of the galvanized sheet, by a brushing or rubbing operation, the soft puttylike amalgam being brushed or rubbed onto the cleaned area of the sheet with a cloth, or in a similar manner. This rubbing or brushing operation spreads the zinc-mercury amalgam over the cleaned area of the sheet and causes a thin layer thereof to adhere to the outer surface of the zinc coating on the sheet. In case there is a rupture or a damaged area in the sheet, from which the zinc has been entirely, or substantially entirely, removed, the zinc-mercury amalgam will adhere to the sheet at this ruptured area also. 'Ihe amalgam, as soon as it contacts the zinc coating on the sheet, begins to act thereon to amalgamate the zinc on the sheet with some of the mercury in the amalgam. Due to the brushing of the amalgam back and forth over the ruptured area, the composition ofthe coating atthe ruptured area will tend to be substantially the same as on other portions of the sheet to which the amalgam is applied. Any loose flakes, or particles, of zinc will be dissolved in the amalgam, amalgamating with the mercury in said amalgam.

The action between the zinc-mercury amalgam and the zinc on the sheet will continue until the amalgam has penetrated the entire zinc coating of the sheet, at least down to the ferrous zinc alloy at the surface of the iron or steel of the sheet. After the zinc on the sheet amalgamates with the mercury, the resulting amalgam will gradually become stiffer and harder, as the greater the amount of other metal amalgamated with the mercury the harder and stiffer the amalgam will become. As a result, the penetration of the zinc on the sheet by the zinc-mercury amalgam, will eventually produce a zinc-mercuryr amalgam throughout the coating on the sheet,

which will have lost the soft character that the zinc-mercury. amalgam had when applied and will become as hard as the zinc coating originally on the sheet.

Thus,. while the amalgam, when first placed on the sheet, will be soft enough that it can be rubbed off on the fingers to a certain extent, after at least twenty-four hours, the coatingat the area to which the amalgam has been applied will be hard enough that none of the same Will rub olf and the sheet can be handled without any damage to the coating thereon, just as readily as was the case with the zinc coating on the sheet originally. The sheet will, after the coating has become hard, have substantially the sameappearance as it did before any amalgam was applied thereto, and none of. the coating can be rubbed oiT, even though it may be rubbed persistently for a considerable period of time. The coating will have the characteristic Spangledl appearance of the zinc coatingoriginally on the sheet. This indicates that the application of the putty-like amalgam to the sheet that has been previously galvanized, while resulting in the dissolving of the zinc on the sheet, in the mercury of the amalgam, does this in such a gradual manner that the liquefactionof the coating material on the sheet takes place at such a slow rate through the thickness of the zinc coating, that the structure of 'the zinc coating on the sheet is not altered, ,although the composition changes from substantially pure zinc to a zinc-mercury amalgam, as the amalgamating process proceeds through the coating. The sheet will accordingly have substantially the same appearance two or` three days after the amalgam was applied thereto as it had before any Aapplication of amalgam thereto.

It is obvious that it may be desirable to not only prevent corrosion at ruptures in coatings on galvanized sheets at bends in such sheets', or similar places, but that the entire area of a sheet,

` or the entire inner surface of a sheet, or section of a container, for example, that is innermost when it is in place, and which is subjected to the corrosive action of sulphuric acid, or other compounds, which are ordinarily found in oil tanks, or similar receptacles, may be provided With a corrosion resisting amalgam coating. By utilizing my protective coating, the corrosive action, caused by these sulphur compounds, on the zinc coating of the sheet ordinarily occurring will be reduced and substantially eliminated, the zincmercury amalgam being applied to the inner surface of such oil tank, or the sections of such an oil tank; made up of sheets lthat have been bent, cut and punched before the application of the amalgam thereto.

The tendency of the sulphur compounds, when acting on the amalgam coating described, is to cause the mercury in the amalgam to forma protective film on the surface that vis exposed to the action ofthe dilute sulphuric acid, or hydrogen sulphide, or other sulphur compounds, this causing some slight loss of some of the zinc, but the mercury arresting this substantially immediately,`

due to its nlm forming action.

While it is immaterial whether `the amalgam which it was -applied at rst, this being on the top surface of the coating. However, if the amalgam above referred 'to is left in contact with the zinc coating for twenty-four hours or more', and an excessive amount of the amalgam is not used, suflicient of the mercury will amalgamate with the zinc that all of the zinc will become' amalg'amated with the mercury, and the resulting coating will be a zinc-mercury amalgam from the outer surface of the coating to at least the ferrous zinc alloy at the surface of the metal of the sheet. The amalgamation of the mercury with the zinc on the sheet, when completed, causes the coating to have a hard character, because there is so much larger apercentage'of zinc in the coating, than there Was in the amalgam applied to the sheet, and the coating will have 'a hard character, similar to that Vof the zinc, instead of a soft putty-like character, such as the zinc-mercury amalgam, that was applied to the amalgam resulting will contain .approximately zinc and 10% mercury. With heavier coatings of zinc, the percentage of zinc will, of course, be higher. `Thus zinc coatings as thick as two and one-half ounces per running square foot,-

have been utilized on galvanized sheets, and for such coatings the resulting amalgam on the sheet will contain about 95,6% zinc, and 4.4% mercury. The putty-like amalgam is applied only thick enough to completely coat the sheet and, of course, with a heavier zinc coating the -resulting amalgam would contain a much smaller percentagev of mercury than where sheets with lighter coatings of zinc are treated to produce my improved amalgam coating. As some variation can also be practicedin the vpercentages,

of zinc or mercury in the putty-like amalgam, depending upon temperature conditions, it has been found that the amount of zinc can b'e varied between 10% and 20% and said putty-like coating materials produced for application to the sheet to produce the amalgam that eventually is formed on said sheet. Due to these variations,

the percentage of zinc finally on the sheet where the amalgam coating is provided thereon will range between 89% and 96%, while the percentage lof mercury will rangebetwee'n 11% and 4%. In all cases, the amalgam resulting that is on the sheet will contain well over 50% zinc and the coating will not lose the characteristics of a zinc coating, except in part, but will be modified to some extent in its characteristics by the mercury contained therein, the mercury acting to make the coating more resistant to corrosion'than the zinc coating was originally. Such a zinc mercury amalgam coating on a sheet is particularly desirable where it is preferred that no lead, or tin, or other metal than zinc and mercury, be present on the surface of the sheet. While the zinc will tend to dissolve under the same circumstances in which it would dissolve on an ordi- .nary galvanized sheet, in a sheet that is provided with an amalgam coating, such as described herein, the mercury in the-amalgam acts to arrest this action on the zinc and causes the zinc-mercury amalgam coating to have a much longer life than a pure zinc coating would have.

Itis highly desirable that the Spangled appearnsA A ance of the coating on the sheet, such as it has when galvanized, be maintained, as this coating has a desirable appearance from the standpoint of the user, and due to the familiarity of the user with the spangled appearance of galvanized sheets, any destruction of this appearance is found to be objectionable from a commercial standpoint.

What I claim is:

1. A galvanized sheet having a coating of zinc and mercury containing from eight to sixteen parts of zinc to one part of mercury by weight on one side thereof, said coating having at least as great a proportion of mercury at its exposed surface as adjacent the metal of the sheet.

2. A galvanized sheet having a bend therein l and having a coating of zinc and mercury containing from eight to sixteen parts of zinc to one' `part of mercury by Weight on the side thereof 4. A galvanized sheet having a bend therein and having a mercury-zinc amalgam coating on the inside thereof lying on the outside of said bend at and adjacent said bend, said coating having at least as great a proportion of mercury at its exposed surface as adjacent the metal of the sheet and having a much greater proportion of zinc than mercury therein.

5. A fabricated steel sheet having a zinc galvanizing coating therein, said zinc coating having interruptions therein, and a zinc-mercury amalgam coating thereon over and adjacent the interruptions in said. zinc coating, said amalgam coating having at least as great a proportion of mercury at its exposed surface as adjacent the metal of the sheet and having a much greater proportion of zinc than mercury therein.

6. A galvanized metallic sheet having a zinc coatingon a portion of the areathereof and a coating of an amalgam composed of zinc and mercury on the remainder of the area thereof, said amalgam coating having at least as great a proportion of mercury at its exposed surface as adjacent the vmetal of the sheet and having a much greater proportion of zinc than mercury therein.

HENRY L. KOHLER.